With so many possible symptoms, hysteria was often [ when? ] considered a catchall diagnosis where any unidentifiable ailment could be assigned. [ citation needed ] As diagnostic techniques improved, the number of ambiguous cases that might have been attributed to hysteria declined. For instance, before the introduction of electroencephalography , epilepsy was frequently confused with hysteria.  Many cases that had previously been labeled hysteria were reclassified by Sigmund Freud as anxiety neuroses .  As a result, theories relating to hysteria came from pure speculation. Doctors and physicians could not connect symptoms to the disorder, causing it to decline rapidly. 
MAOIs started off due to the serendipitous discovery that iproniazid was a potent MAO inhibitor (MAOI).  Originally intended for the treatment of tuberculosis, in 1952, iproniazid's antidepressant properties were discovered when researchers noted that the depressed patients given iproniazid experienced a relief of their depression. Subsequent in vitro work led to the discovery that it inhibited MAO and eventually to the monoamine theory of depression . MAOIs became widely used as antidepressants in the early 1950s. The discovery of the 2 isoenzymes of MAO has led to the development of selective MAOIs that may have a more favorable side-effect profile.